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New Liquid Crystalline Materials: Experimental and Computational Approaches

A special issue of Molecules (ISSN 1420-3049). This special issue belongs to the section "Applied Chemistry".

Deadline for manuscript submissions: closed (31 May 2023) | Viewed by 6252

Special Issue Editor


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Guest Editor
Faculty of Science, Chemistry department, Cairo University, Cairo, Egypt
Interests: liquid crystals; supramolecular chemistry; azopyridine; azomethine; optical parameters; physical and thermal parameters; computational calculations; quantum chemistry
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

One of the most interesting features of liquid crystalline materials is their molecular structure and optical characteristics. Due to their potential for applications in technologies related to material science, they have recently been the subject of significant research. Since the discovery of liquid crystal phases, their types and properties have become increasingly significant in a variety of commercial and academic fields. Because they combine a number of useful properties, such optical transparency, high birefringence, and high sensitivity to electric, light, and thermal fields, liquid crystalline materials are actively being developed for applications in optics and photonics.

Liquid crystalline materials' optical qualities are primarily influenced by their molecular geometry, and even small alterations in their molecule structure can significantly impact both their mechanical and optical properties. An significant area of interest for geometrical techniques is the modification of particular materials to develop innovative buildings. Several synthetic compounds have been created in recent years to create a wide range of molecular geometries. Among these characteristics are polymeric structures, symmetric dimers, non-symmetric dimmers, and molecules with rod-like and angular shapes, each of which has its own unique mesophase.

Research dealing with the problems relating to optical properties, physical and thermal characterizations, structure, dynamics, interactions, reaction mechanisms, and reaction rates, and that involving new synthesized materials, nanostructures, soft matter, self-assembly, and composites, is invited for submission.

This Special Issue, “New Liquid Crystalline Materials: Experimental and Computational Approaches”, aims to provide an open multidisciplinary platform for new research on chemistry, material science, and possible applications of soft materials as well as their geometrical approaches.

Dr. Hoda A. Ahmed
Guest Editor

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Keywords

  • liquid crystals
  • optical parameters
  • physical characterizations
  • thermal parameters
  • supramolecular chemistry
  • computational calculations
  • molecular geometry
  • metallomesogens

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Published Papers (3 papers)

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Research

13 pages, 1636 KiB  
Article
Synthesis of New Liquid-Crystalline Compounds Based on Terminal Benzyloxy Group: Characterization, DFT and Mesomorphic Properties
by Alaa Z. Omar, Mohammed L. Alazmi, Mai S. Alsubaie, Ezzat A. Hamed, Hoda A. Ahmed and Mohamed A. El-Atawy
Molecules 2023, 28(9), 3804; https://doi.org/10.3390/molecules28093804 - 28 Apr 2023
Cited by 15 | Viewed by 1940
Abstract
The effect of the terminal benzyloxy group on the mesomorphic properties of liquid crystalline materials developed from rod-like Schiff base has been described. For this objective, a novel Schiff base liquid crystal family, specifically new series of Schiff base liquid crystals, namely, ( [...] Read more.
The effect of the terminal benzyloxy group on the mesomorphic properties of liquid crystalline materials developed from rod-like Schiff base has been described. For this objective, a novel Schiff base liquid crystal family, specifically new series of Schiff base liquid crystals, namely, (E)-4-(alkyloxy)-N-(4-(benzyloxy)benzylidene)aniline, In, are prepared and investigated in detail. The length of the terminal alkyloxy chain (n) varies amongst the compounds in the series. Where n varies between 6, 8 and 16 carbons. At the other end of the compounds, benzyloxy moiety was attached. The molecular structures of all synthesized compounds were established using different spectroscopic techniques. The molecular self-assembly was explored using differential scanning calorimetry (DSC) and polarized optical microscope (POM). Depending on the length of the terminal alkyloxy chain, only one type of SmA phase with different stability was observed. The previously reported para-substituted systems and the present investigated compounds were compared and discussed. The calculated quantum chemical parameters were computationally correlated using the DFT method via the B3LYP 6-311G(d,p) basis set. The theoretical computations revealed that the length of the alkyl side chain influences the zero-point energy, reactivity and other estimated thermodynamic parameters of benzoyloxy/azomethine derivatives. Furthermore, the FMO energy analysis shows that molecule I16 have higher HOMO energies than the other compounds, and I6 has a much lower LUMO level than the rest. Full article
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12 pages, 3456 KiB  
Article
Fluorination Improves the Electro-Optical Properties of Benzoxazole-Terminated Liquid Crystals in High Birefringence Liquid Crystal Mixtures: Experimental and Theoretical Investigations
by Ran Chen, Zihao Mao, Zhongwei An, Xinbing Chen and Pei Chen
Molecules 2023, 28(7), 3019; https://doi.org/10.3390/molecules28073019 - 28 Mar 2023
Viewed by 1874
Abstract
Aromatic heterocyclic liquid crystal (LC) materials have received much attention from LC chemists for their high birefringence and large dielectric anisotropy, yet few have reported their properties in LC mixtures. In this work, a series of fluorinated benzoxazole liquid crystal compounds were synthesized [...] Read more.
Aromatic heterocyclic liquid crystal (LC) materials have received much attention from LC chemists for their high birefringence and large dielectric anisotropy, yet few have reported their properties in LC mixtures. In this work, a series of fluorinated benzoxazole liquid crystal compounds were synthesized to evaluate their electro-optical properties in high birefringence LC mixtures, with the expectation of further establishing the theoretical basis and experimental evidence for their applications in LC photonics. Firstly, the effects of the lateral fluorine substituent positions on the molecular synthetic yield, mesomorphic and solubility properties were comparatively investigated. Afterwards, we focused on the fluorination effects on the core electro-optical properties, including birefringence, dielectric anisotropy and further investigation of the viscoelastic coefficient of high birefringence LC mixtures. Research results showed that the benzoxazole liquid crystal compounds possess low melting points, wide nematic phase intervals and good solubility by appropriate lateral fluorine substitution, which is beneficial to further improve the electro-optical properties of high birefringence LC mixtures. Meanwhile, the theoretical and experimental results corroborate each other to well reveal the structure–property relationship. This study demonstrates that fluorination would promote promising applications of benzoxazole-terminated liquid crystals in emerging LC optical devices. Full article
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14 pages, 3031 KiB  
Article
Design of Liquid Crystal Materials Based on Palmitate, Oleate, and Linoleate Derivatives for Optoelectronic Applications
by Salma A. Al-Zahrani, Mohd Taukeer Khan, Violeta Jevtovic’, Najat Masood, Yassin Aweis Jeilani and Hoda A. Ahmed
Molecules 2023, 28(4), 1744; https://doi.org/10.3390/molecules28041744 - 11 Feb 2023
Cited by 8 | Viewed by 2047
Abstract
Herein, liquid crystalline derivatives based on palmitate, oleate, and linoleate moieties with azomethine cores were synthesized, and their physical, chemical, optical, and photophysical properties were investigated in detail. The mesomorphic activity of these materials was examined through polarized optical microscopy (POM) and differential [...] Read more.
Herein, liquid crystalline derivatives based on palmitate, oleate, and linoleate moieties with azomethine cores were synthesized, and their physical, chemical, optical, and photophysical properties were investigated in detail. The mesomorphic activity of these materials was examined through polarized optical microscopy (POM) and differential scanning calorimetry (DSC). The observed results revealed that the stability of the thermal mesophase depends on the terminal polar as well as on the fatty long-chain substituents. Purely smectogenic phases were detected in all three terminal side chains. A eutectic composition with a low melting temperature and a broad smectic A range was found by constructing a binary phase diagram and addressing it in terms of the mesomorphic temperature range. The energy bandgap of the palmitate-based derivative (Ia) was determined as 3.95 eV and slightly increased to 4.01 eV and 4.05 eV for the oleate (Ib) and linoleate (Ic) derivatives, respectively. The optical constants (n, κ, εr, and εi) were extracted from the fitting of measured spectroscopic ellipsometer data. The steady-state spectra of these samples exhibited a broad emission in the range 400–580 nm, which was found to be blue shifted to 462 nm for both Ib and Ic derivatives. The average fluorescence decay lifetime of the Ia derivative was found to be 598 ps, which became faster for the Ib and Ic derivatives and slower for the sample with a chloride end polar group. Full article
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